"""
The following code replicates an HTTP client exiting upon receiving
an unexpected response from the server, in this case a 401 status
when a keystone token is either missing or invalid. The status is
being evaluated before the entire HTTP response has been retrieved
and the client exits, destroying the socket to the server.

On the server side the server is unable to send its remaining data to
the client and produces errors similar to:

    error: [Errno 32] Broken pipe

There are two potential fixes for when this sort of thing is going,
both on the client side:

    * Send a valid keystone token
    * Accept a 401 response as a valid indicator of a healthy server
      (You'll only ever get a 401 when _something_ intelligent is there).

In addition an HTTP client (the thing sending the OPTIONS) should not
treat a 401 response as a catastrophic error and raise an untrapped
exception (and thus exit). Instead the socket should be closed gracefully:
the conversation with the server was _valid_ it just wasn't what was desired.

The problem only appears to show up when there are concurrent requests and
the eventlet handling gets confused. You can stimulate the problem by running
this script in parallel.

    for in in {1..20}; do echo $i; python /tmp/request.py & done

The upshot of all this is that health check clients needs to be careful about
behaving as reasonable HTTP clients.
"""


import socket
import sys
import time

def do(nasty=True):
    # Open a request to the ceilometer api and make a minimal
    # OPTIONS request.
    clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    clientsocket.connect(('localhost', 8777))
    clientsocket.send('OPTIONS / HTTP/1.1\n')
    clientsocket.send('X-Auth-Token: amazing\n\n')

    # A place to accumulate the response
    cache = []
    # Read one single byte
    atom = clientsocket.recv(1)
    # Loop reading one byte until we note the 401, then exit
    # violently without cleaning receiving all the response.
    while atom:
        if atom == '1' and cache[-2:] == ['4', '0']:
            print '#### GOT 401'
            if nasty:
                sys.exit(1)
        cache.append(atom)
        atom = clientsocket.recv(1)

if __name__ == '__main__':
    for i in range(5):
        print '### TRY', i
        do()